HTC Backup has been renamed as HTC Restore. With this service, you can restore previous backups saved by HTC Backup to your phone.
You need to download and use the HTC Restore app on your phone to access these backups.
Starting from Android 6.0, use the Android
Backup Service to automatically back up your phone to Google Drive. Also use this service when restoring your backup from Google Drive to a new phone.
See the user guide or how-tos for details.